Combustion apparatus



Gd. 9, i945 D. J. MOSSHART 235,336

COMBUSTION APPARATUS Y y Filed June l2, 3,941

0 a l d' ATTORNEY www vPatented Oct. 9, 1945 y oi-'FicE coMnUs'rroNAPPARATUS Y,

Donald '.r. Masami, Ardmore,

Pa.. asslxnor to Westinghouse Electric Corporation, East Pittsbur-gh,Pa., a corporation of Pennsylvania Application June 12, 1941, Serial No.397,670

2 Claims. (Ci. 110-40) The invention relates to a furnace and method ofoperating the same, wherein the fuel is fed to a progressive feedsto'kerby means loi a spreader or sprinkler.

An object of the invention isto so control theA heating and combustionof the sprinkled fuel during its travel from the feeder to the gratethat the fuel is deposited on the grate in a spongy. loose. lightlyagglutinated which air will readily flow but which will, because of itspartial agglutination, resist being carried away by the air flowingthrough the grate in the latter stages of combustion.

Another object of the invention is to limit the deposition of the fuelon the fuel bed to a limited first portion thereof, and restricting theflow of air to that portion to an extent sumcient to prevent the fuelbeing lifted from the fuel bed and to prevent the particles of the fuelbeing sprinkled thereon from beingcarried away in the gases rising fromthe fuel bed.

Yet another object of the invention is to so operate a chain ortraveling grate stoker that the fuel is deposited on a limited portionthereof by a spreading or sprinkling device in such manner that the fuelbed tapers nothing at the extreme front encl'to a maximum at the rearend of the fuel-sprinkling portion, and then tapers to nothing at therear or ashdischarge end thereof,

A further object of the invention is the provision, in a spreader-fedchain grate Stoker of pressure-responsive means for maintaining apredetermined ratio between rate of feed of fuel to the grate and rateof flow of air to the fuel-fed portion of the grate.

These and other objects are edected by the invention as will be apparentfrom the following description and claims taken in connection with theaccompanying drawing, forminga part of this application, in which thesingle figure is a vertical sectional view taken through a furnace andStoker installation constructed in accordance with the presentinvention.

Referring now to the drawing more in detail, there is shown at i afurnace comprising front and rear walls li and i2, respectively, andside walls i3. A suitable progressive feed stoker i5 is provided in thelower portion of the furnace, which, in the arrangement hereinillustrated, is a chain grate st oker, of conventional construction.Fuel is fed to thegrate l5 from a hopper i8 located externally of thefurnace l by means such as the ram il and spreader i8, both driven froma suitable source of power, such as the bed or mass throughl inthickness from variable-speed motor i9, by belts 20 and 2i,respectively. A conventional ash pit 23 is provided beneath the rear ordischarge end of the stoker for reception of ash and other refusedischarged fromy the traveling grate.

In accordance with the present invention, the usual plenum chamber 25 isdivided by a partition structure 26 and 21' into a first compartment at28 and a second compartment at 29. Air under pressure is supplied to 30,by way of the passages 3i and 32, respectively. In order to control thesupply of air to the compartment 28, there is provided a meteringorifice 3d followed by a damper 35. Pressure-responsive apparatus, at36, provides for variation in the flow of air to the compartment 28 indirect proportion to variations in the quantity of fuel fed to thegrate.

To this end, the motor i9 is directly connected a tachometer blower 3lwhich supplies air under pressure to a bellows 3d, the latter beingconnected through the compression spring t@ to one end of a lever te,pivotally mounted intermediate its ends on a fixed support at ll. Thecompression spring 3d. whose tension may be adjusted by the screw di,urges the right-hand end of the lever lll upwardly with respect to thebellows 3d. The left-hand end ofthe lever d@ is connected through therod l5 to a pair of spaced bellows 13B and tl, the former being incommunication with the upstream side of the metering orifice 343 and thelatter being in communication with the downstream side thereof. Thelever d@ is also connected through the stem 5i with the valve 52controlling flow of pressure medium through the conduit 53, the latterbeing in communication with the expansible chamber 5t. One wall of thischamber is defined by the movable piston 55, which is connected by therod 56 with the bellcrank 5l, xedly secured to the damper 35 in thepassage 3i. A compression coil spring 59 urges the movable wall 55 ofthe chamber 5t into contracted or collapsed position.

The partition structure 2B and 2l, which divides the plenum chamber 25into the compartments 28 and 2t.' is so disposed as to, in effect,

divide the grate surface and the atmosphere thereabout into first andsecond zones, A and B, respectively. The particular percentage of thegrate surface occupied by each of these two zones will be dependentup'on varying conditions of operation, particularly the type of fuelbeing burned. With a number of fuels, the first zone A would constituteapproximately Y40% of the fuel-supthe compartments 28 and 29 from anysuitable source, such as the blower porting surface, and the zone Bwould make up the remaining 60% of the surface, However, under otherconditions, the first zone A might vary from 30 to 60% of the totalgrate surface.

According to the improved method of operation, it is proposed to projectthe fuel onto the first zone of the grate through the hot atmos- I phereabove that zone, with the result that lthe fuel is partially ignited anddeposited upon the grate as a light, spongy and partly agglutinatedmass. In order to obtain this result, it is found necessary to limit thesupply of air fed to this first zone to such an extent that the tendencyfor particles of fuel to be carried off the fuel bed is minimized and sothatv the air rising from this section of the bed is of insufficientvelocity to prevent the sprinkled fuel from falling therethrough to thebed rather than for the lighter portions thereof to be caught andcarried away in suspension by the rising gases. Thus, by operating thefirst zone A with a deficiency of air, the latter operates, in effect,as a gas producer or coking portion. 4

Substantially complete combustion of this partially-coked fuel iscompleted in the second zone B of' the grate. In the event thatinsufficient air is supplied to this second zone B to produce completecombustion of the fuel thereon, secondary air may be supplied to theatmosphere immediately overlying the second zone through ducts 60 andconduits 6I associated with the rear wall I2 of the furnace.`

If it is found that, due to improper operation, any considerablequantity of fuel particles are carried into the boiler structure by thecombustion gases, means, such as the hopper 62, may be provided forreturning the particles to the combustion chamber. To this end, there isprovided a conduit 63 from the secondary air duct 6D, which terminatesin an ejector nozzle G4, aligned with the inlet end of the conduit Bi.It will be apparent that, with this arrangement, the secondary air fromthe duct 60 will serve to convey the fuel particles from the hopper 62to the combustion chamber. Preferably, this secondary air is suppliedunder sufficient force to carry the fuel particles across the zone B andinto the atmosphere of zone A, where the restricted flow of air willpermit these particles to settle for normal consumption upon the fuelbed.

If desired, further means for supplying secondary air may be provided inthe form of a second duct 66 and delivery ducts 61 associated with thefront wall l l of the furnace.

While the invention has been shown in but one assenso form, it will beobvious to those skilled in the art that it is not so limited, but issusceptible of various changes and modifications without departing fromthe spirit thereof, and it is desired,

Itherefore, that only such limitations shall be placed thereupon as arespecifically set forth in the appended claims.

What is claimed is:

1. A progressive feed stoker providing a fuelsupporting surface having areceiving and nokmg first zone and a combustion and discharging secondzone, considered in the direction of fuel feed; means of the sprinkleror spreader type spaced a material distance above the fuel-supportingsurface and adjacent an edge of the receiving zone, said means spreadingthe fuel uniformly over the first zone only of the fuel-supportingsurface through the hot atmosphere above said first zone only, to heatand ignite said fuel before it is deposited on the surface; a plenumchamber below the stoker for conducting ail to the latter; a partitiondividing said chamber into a first space communicating with the firstzone and a second space communicating with the second zone; andpressure-responsive means for maintaining a, predetermined ratio of rateof flow of fuel to rateof flow of air to the first zone, whereby theremay be provided on said first zone a loose, partially coked and ignitedfuel bed adapted to be consumed on the second zone.

2. A progressive feed stoker providing a fuelsupporting surfaceextending from front to rear thereof and having a front fuel-receivingand coking zone and a rear fuel-consuming and discharging zone;fuel-feeding means of the sprinkler or spreader type spaced a materialdistance above the fuel-supporting surface and adjacent the front edgeof the front fuel-receiving and coking zone, said means spreading thefuel uniformly over the first zone only through the atmosphere abovesaid first zone only, whereby said fuel is heated and at least partiallyignited before being deposited on said first zone; a plenum chamberbelow the Stoker for conducting air to the latter: a partition dividingsaid chamber into a first space communicating with the front zone and asecond space communicatingwith the rear zone; and pressure-responsivemeans for maintaining a predetermined ratio of rate of flow of 'fuel torate of -ow of air to the front zone,

whereby there may be provided on said front zone a partially coked andignited fuel bed adapted to be consumed on the rear zone.

DONALD J. MOSSHART.

